JPH0645478B2 - Infrared transparent glass fiber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention shows good infrared transmittance up to a long wavelength region,
Especially in industry, as materials for sensors and optical waveguides,
The present invention relates to a glass material which reaches the production of an infrared transmissive fiber having a low loss light transmission window in a wavelength range of 12 μm.

[Prior Art] Conventionally, as an infrared transparent glass material, a chalcogenide glass containing a chalcogen element as a raw material has been considered promising. Examples of chalcogenide glass include As-S
And / or Se-based glass, Ge-S and / or Se-based glass and Ge-As-Se-Te-based glass fiber, etc.,
Materials containing Ge, As, S, Se, Te, etc. in their composition have been investigated. However, these infrared-transmissive glass fibers have drawbacks in that
At present, it is not possible to obtain low-loss light transmission at a thickness of μm or more.

[Problems to be Solved by the Invention] Chalcogenide glass elements S, Se, Te and G
In the chalcogenide glass fiber containing e and As as composition components, the light transmissivity in the long wavelength region is limited by the multiphonon absorption of lattice vibration of As-S or Se bond, Ge-S or Se bond. . For example, wavelengths of 6 μm or more for As-S glass fiber, 8 μm or more for Ge-Se glass fiber, 9 μm or more for Ge-As-Se glass fiber, and 10 μm or more for Ge-As-Se-Te glass fiber. In the present situation, the optical loss is limited by the multiphonon absorption due to the bond between the raw material elements described above in the region, and it is practically difficult to provide an optical fiber having a low loss in a longer wavelength region.

Therefore, the object of the present invention is to have light transmission in the long wavelength region,
Moreover, a stable infrared-transmissive material that does not crystallize during fiber spinning is provided to provide a long glass fiber with low loss using the above glass material.

[Means for Solving the Problems] In order to achieve the above object, the present invention has a composition ratio of S
e is 20 to 70 at.%, Te is 10 to 40 at.% and I is 20 to 48 a.
It is achieved by using a chalcogenide glass which is composed of t.% and whose total composition ratio is 100 at.%.

Regarding the Se-Te-I chalcogenide glass described here, J. Lucas et al.
E "Volume 843, Infrared Optical Materials and Fibers V" (J. Lucas et al.
SPIE Vol.843 infrared optical Materials and Fibers
V (1987) P.2), but no study has been made on the stable composition range that can withstand fiber spinning and the like. The present invention is to obtain a glass fiber having a low loss in a long wavelength region by limiting the above composition ratio.

The infrared transmittance of the chalcogenide glass is limited by the lattice vibration due to the bond between the raw material elements forming the glass matrix. The chalcogenide glass containing As and / or Ge as a raw material element is, for example, As—S or Se bond, Ge.
Infrared transmission at long wavelengths is determined by the multiphonon absorption inherent in glass based on -S or Se coupling. Therefore, in order to reduce the optical loss in the long wavelength region, it is necessary to move the absorption due to the lattice vibration peculiar to glass to the long wavelength side. The frequency (ν) of this lattice vibration is inversely proportional to the atomic weight of the glass-constituting element, and therefore the wavelength of the lattice vibration (λ = c /
ν) is proportional to the atomic weight of the glass-constituting element, and the larger the atomic weight of the glass-constituting element, the more the wavelength shifts to the longer wavelength side.

The raw material element of the chalcogenide glass provided in the present invention does not include elements having a smaller atomic weight than the Se (atomic weight 78.96) element, such as S (atomic weight 32.06), Ge (atomic weight 72.59) and As (atomic weight 74.92), Since it is composed of the chalcogenide element Te (atomic weight 127.6) and the halogen element I (atomic weight 126.9), which have a large value, it is possible to shift the multiphonon absorption due to the lattice vibration of the glass base material to the long wavelength side. Therefore, it is possible to produce glass with low loss in the long wavelength region. Further, by spinning the above-mentioned glass, it becomes possible to prepare an infrared transmitting fiber having a low loss in a long wavelength region. Especially, carbon dioxide laser wavelength
To achieve the objective of lowering the loss at 10.6 μm,
S that contains the largest amount of elements with a large atomic weight that shifts multiphonon absorption to the long wavelength side in the stable vitrification region that can be spun
e ₂₅ ± _2.5 Te ₃₀ ± _2.5 I ₄₅ ± _2.5 It is desirable to achieve within the composition range.

In the stable vitrification region shown in FIG. 1, particularly when synthesizing the glass having the composition shown in FIG. 2, performing fiber spinning, and examining the state and loss value of the glass and fiber,
With a composition ratio of Se ₂₅ Te ₃₀ I ₄₅ as the center, the Se content is 2
Even if it exceeds 7.5at%, the loss value is at least higher than 22.5at%. Further, when the Te content is reduced, the glass is crystallized during glass synthesis, or the fiber is devitrified during spinning. On the contrary, it was found that the loss value increased due to scattering as the number increased. It was also found that when the I content increases, the glass tends to crystallize, and conversely, when the I content decreases, the loss value increases. Therefore, the glass composition showing the lowest loss at the carbon dioxide laser wavelength is limited to the range of Se ₂₅ ± _2.5 Te ₃₀ ± _2.5 I ₄₅ ± _2.5 centered on the Se ₂₅ Te ₃₀ I ₄₅ composition in Fig. 2. It

[Operation] The glass composition that constitutes the infrared permeable optical fiber material of the present invention has multi-phonon absorption due to lattice vibration on the long wavelength side, and can transmit infrared rays in the long wavelength region with low loss.

[Examples] Examples of the present invention will be described below.

Purity 99.99999% so that the specified composition ratio shown in Table 1 is obtained.
Se, 99.99999% pure Te and 99.999% pure I raw material were mixed and placed in an anhydrous quartz glass ampoule (inner diameter 10 mmφ, wall thickness 2.5 mm, length 150 mm) that was exhausted while heating.
After filling in an argon gas atmosphere, it was vacuum-sealed at a vacuum degree of 10 ⁻⁵ Torr. A quartz glass ampoule containing this glass raw material was heated and melted and synthesized at 700 ° C. for 40 hours in an agitation furnace, then taken out of the furnace and rapidly cooled to room temperature to obtain a glass rod.

In order to evaluate this glass, differential scanning calorimetry was carried out at a scanning temperature of 10 ° C./min to examine the presence or absence of a crystallization peak. FIG. 1 shows a stable vitrification region in which no crystallization peak is observed in the thermal analysis of the Se—Te—I chalcogenide glass determined in this example. The vitrification region in which no crystallization peak is observed exists in a wide range, and the degree of freedom in composition selection is wide, and it is shown that the Se-Te-I chalcogenide glass is a stable glass system. Further, since no crystallization peak is observed in the glass in the vitrification region, it is shown that a good optical fiber can be produced without causing crystallization during fiber spinning.

As an example, the above-mentioned glass in the stable vitrification region was prepared, and the obtained glass lot with a length of 60 mm and a diameter of 10 mm was spun from a quartz glass nozzle at a pressure of 0.5 kg / cm ² to prepare an optical fiber. I investigated the loss. Table 1 shows the minimum loss value of the obtained glass fiber, the wavelength at that time, and the loss value at the carbon dioxide laser wavelength of 10.6 μm. In particular, it can be seen that the glass fiber having the composition of Se ₂₅ Te ₃₀ I ₄₅ in the desirable range described above has the lowest loss.

From this example, if the composition is selected from within the stable vitrification region, it is possible to prepare an infrared-transmissive optical fiber having a low loss at a target wavelength. FIG. 3 shows the wavelength-loss characteristic of the glass fiber of the composition Se ₂₅ Te ₃₀ I ₄₅ with the least loss. At 10.6 μm, the loss value was 0.9 dB / m.

[Effects of the Invention] As described above, the composition in the chemical conversion region of the Se-Te-I-based chalcogenide glass glass shown in FIG. 1 does not crystallize during fiber spinning, and a long and stable glass fiber is obtained. Can be created. Moreover, it is a light-transmitting material that satisfactorily transmits infrared rays in the long wavelength region. In addition, since it is possible to create a fiber with low loss at a carbon dioxide laser wavelength of 10.6 μm, it has the advantage that it can be used as a laser optical waveguide and as a glass material for infrared transmission such as a sensor that uses infrared rays or optical communication. is doing.

[Brief description of drawings]

FIG. 1 is a diagram showing a stable vitrification region of Se-Te-I chalcogenide glass, and FIG. 2 is a glass composition centered on the Se ₂₅ Te ₃₀ I ₄₅ composition and a carbon dioxide laser wavelength of 10.6 μ.
FIG. 3 is a graph showing a loss value at m, and FIG. 3 is a graph showing wavelength-loss characteristics of a glass fiber having a composition of Se ₂₅ Te ₃₀ I ₄₅ .

Claims (2)

[Claims] 1. A glass composition containing 20 to 70 at.% Of Se,
An infrared-transmitting chalcogenide glass fiber, characterized in that Te is 10 to 40 at.% And I is 20 to 48 at.%, And the total composition ratio thereof is 100 at. 2. A glass composition of Se ₂₅ ± _2.5 Te ₃₀ ± _2.5 I ₄₅
The infrared-transmissive chalcogenide glass fiber according to claim 1, which has a _density of ± _2.5 .